Method of manufacture of a bend actuator direct ink supply ink jet printer

ABSTRACT

A method of manufacture of a thermally actuated ink jet printer which ejects ink via the utilization of a thermal actuator device is disclosed comprising the steps of initially providing a silicon and circuitry wafer layer including electrical circuitry necessary for the operation of the thermal actuators on demand; depositing a first sacrificial layer on top of the silicon and circuitry wafer layer; forming a series of heater structure layers comprising the thermal actuator on top of the first sacrificial layer; depositing a second sacrificial layer on top of the heater structure layers, the second sacrificial layer including suitably etched portions for the forming of a nozzle chamber; depositing a nozzle chamber layer forming a nozzle chamber of the ink jet printer having an ink ejection port defined therein on top of the second sacrificial layer; back etching the silicon wafer layer to form an ink supply channel in a region underneath a moveable end of the thermal actuator; and etching the first and second sacrificial layer in addition to relevant portions of the circuitry layer, if any, so as to release the thermal actuator layers to provide for an operational ink jet printer nozzle supplied via the ink supply channel.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

CROSS-REFERENCED U.S. PAT. NO./PATENT AUSTRALIAN APPLICATION PROVISIONAL(CLAIMING RIGHT OF PATENT PRIORITY FROM AUSTRALIAN DOCKET APPLICATIONNO. PROVISIONAL APPLICATION) NO. PO7991 09/113,060 ART01 PO850509/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO801709/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO803209/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO803109/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO797909/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO798209/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO798009/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO801609/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO793909/112,785 ART29 PO8501 09/112,797, 6,137,500 ART30 PO8500 09/112,796ART31 PO7987 09/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090ART34 PO8020 09/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786ART42 PO8000 09/113,051 ART43 PO7977 O9/112,782 ART44 PO7934 09/113,056ART45 PO7990 09/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753ART48 PO7981 09/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054ART52 PO8026 09/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757ART56 PO9394 09/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829ART59 PO9398 09/112,792 ART60 PO9399  6,106,147 ART61 PO9400 09/112,790ART62 PO9401 09/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795ART65 PO9405 09/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783ART69 PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834Fluid01 PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO806609/112,751 IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO807109/112,803 IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO804409/113,084 IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO805609/112,779 IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO803609/112,818 IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO806709/112,819 IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO803309/113,068 IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO806209/112,809 IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO804109/113,121 IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO804309/112,794 IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO938909/112,756 IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP089109/112,811, 6,188,415 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36PP0993 09/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39PP2592 09/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42PP3987 09/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45PO7935 09/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03PO8061 09/112,827 IJM04 PO8054 09/112,828 IJM05 PO8065  6,071,750 IJM06PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09PO7933 09/113,114 IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126,6,190,931 IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO807909/113,221 IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO794809/113,117 IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO794109/113,110 IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO805109/113,074 IJM27 PO8045  6,110,754 IJM28 PO7952 09/113,088 IJM29 PO804609/112,771 IJM30 PO9390 09/112,769 IJM31 PO9392 09/112,770 IJM32 PP088909/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37 PP087409/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40 PP259109/112,832, 6,180,427 IJM41 PP3990 09/112,831, 6,171,875 IJM42 PP398609/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP089509/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP088709/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP088609/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP087709/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP088309/112,775 IR19 PP0880  6,152,619 IR20 PP0881 09/113,092 IR21 PO8006 6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04PO8010  6,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO7947  6,067,797MEMS07 PO7944 09/113,080 MEMS09 PO7946  6,044,646 MEMS10 PO939309/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the manufacture of ink jet print headsand, in particular, discloses a method of manufacture of a bend ActuatorDirect Ink Supply Ink Jet Printer.

BACKGROUND OF THE INVENTION

Many ink jet printing mechanisms are known. Unfortunately, in massproduction techniques, the production of ink jet heads is quitedifficult. For example, often, the orifice or nozzle plate isconstructed separately from the ink supply and ink ejection mechanismand bonded to the mechanism at a later stage (Hewlett-Packard Journal,Vol. 36 no 5, pp33-37 (1985)). These separate material processing stepsrequired in handling such precision devices often add a substantialexpense in manufacturing.

Additionally, side shooting ink jet technologies (U.S. Pat. No.4,899,181) are often used but again, this limits the amount of massproduction throughput given any particular capital investment.

Additionally, more esoteric techniques are also often utilised. Thesecan include electroforming of nickel stage (Hewlett-Packard Journal,Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laserablation (U.S. Pat. No. 5,208,604), micro-punching, etc.

The utilisation of the above techniques is likely to add substantialexpense to the mass production of ink jet print heads and therefore addsubstantially to their final cost.

It would therefore be desirable if an efficient system for the massproduction of ink jet print heads could be developed.

Of course, with any ink jet design, it is important to provide aconstruction arrangement as compact as possible.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for the manufactureof an efficient compact form of ink jet printer device.

In accordance with the first aspect of the present invention there isprovided a method of manufacture of a thermally actuated ink jet printerwhich ejects ink via the utilization of a thermal actuator devicecomprising the steps of initially providing a silicon and circuitrywafer layer including electrical circuitry necessary for the operationof the thermal actuators on demand; depositing a first sacrificial layeron top of the silicon and circuitry wafer layer; forming a series ofheater structure layers comprising the thermal actuator on top of thefirst sacrificial layer; depositing a second sacrificial layer on top ofthe heater structure layers, the second sacrificial layer includingsuitably etched portions for the forming of a nozzle chamber; depositinga nozzle chamber layer forming a nozzle chamber of the ink jet printerhaving an ink ejection port defined therein on top of the secondsacrificial layer; back etching the silicon wafer layer to form an inksupply channel in a region underneath a moveable end of the thermalactuator; and etching the first and second sacrificial layer in additionto relevant portions of the circuitry layer, if any, so as to releasethe thermal actuator layers to provide for an operational ink jetprinter nozzle supplied via the ink supply channel.

Preferably, multiple ink jet nozzles are formed on a single wafer andwherein the back etching includes forming a single ink supply channelsupplying multiple different nozzle chambers. Each of the ink supplychannels abuts a nitride wall of the nozzle chamber the nitride walldividing the ink supply channel into multiple supply channels.

The heater structure layers can be formed by the steps of depositing afirst expansive material layer on top of the first sacrificial layer;depositing a conductive heater layer on to of the first expansivematerial layer; and depositing a second expansive material layer on topof the conductive heater layer. The conductive heater layer can beformed from gold utilizing chemical mechanical planarization.

The circuitry layer can preferably include metal conductive lines whichare utilized to from a barrier to protect other portions of thecircuitry layer from unwarranted etching by any sacrificial etchantutilized in etching of the sacrificial layer.

The nozzle chamber layer can ideally include a series of small etchantholes utilized in the etching of the sacrificial layers and can comprisesubstantially Silicon Nitride. The nozzle chamber layer can includeportions formed directly on the heater structure layers which act tofirmly clamp the heater structure layers to lower layers.

In accordance with a further aspect of the present invention, there isprovided a method of manufacturing a bend actuator direct ink supplyprint head wherein an array of nozzles are formed on a substrateutilising planar monolithic deposition, lithographic and etchingprocesses.

Multiple ink jet heads are preferably formed simultaneously on a singlesilicon wafer planar substrate.

The print heads are preferably formed utilising standard vlsi/ulsiprocessing with the integrated drive electronics preferably formed onthe same substrate. The integrated drive electronics may be formedutilising a CMOS fabrication process.

Ink can be ejected from the substrate substantially normal to thesubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIGS. 1-3 illustrate basic operation of the preferred embodiments;

FIG. 4 is a sectional view of the preferred embodiment;

FIG. 5 is an exploded perspective view of the preferred embodiment;

FIGS. 6-15 are cross-sectional views illustrating various steps in theconstruction of the preferred embodiment; and

FIG. 16 illustrates a top view of an array of ink jet nozzlesconstructed in accordance with the principles of the present invention.

FIG. 17 provides a legend of the materials indicated in FIGS. 18 to 29;and

FIG. 18 to FIG. 29 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, a drop on demand ink jet printer isprovided which allows for the ejection of ink on demand by means of athermal actuator which operates to eject the ink from a nozzle chamber.The nozzle chamber is formed directly over an ink supply channel therebyallowing for an extremely compact form of nozzle chamber. The extremelycompact form of nozzle chamber allows for minimal area to be taken up bythe printer head device thereby resulting in an improved economicsfabrication.

Turning initially to FIGS. 1-3, the operation of the preferredembodiments is described. In FIG. 1, there is illustrated a sectionalview of two ink jet nozzles 10, 11 which are formed on a silicon wafereg. 12 which includes a series of through wafer ink supply channels eg.13.

Located over a portion of the wafer 12 and over the ink supply channel13 is a nozzle actuator device 14 which is actuated so as to eject inkfrom the corresponding nozzle chamber eg. 11. The actuator 14 is placedsubstantially over the ink supply channel 13. In the quiescent position,the ink fills the nozzle chamber 11 and an ink meniscus 15 forms acrossthe output nozzle of the chamber 11.

When it is desired to eject a drop from the chamber 11, the thermalactuator 14 is activated by means of passing a current through theactuator. The actuation causes the actuator 14 to rapidly bend upwardsas indicated in FIG. 2. The movement of the actuator 14 results in anincrease in the ink pressure around the nozzle of the chamber 11 whichin turn causes a significant bulging of the meniscus 15 and the flow ofink out of the nozzle chamber 11. The actuator 14 can be constructed soas to impart sufficient momentum to the ink to cause the direct ejectionof a drop. Alternatively, as indicated in FIG. 3, the activation ofactuator 14 can be timed so as to turn the actuation current off at apredetermined point so as to cause the return of the actuator 14 to itsoriginal position thereby resulting in a consequential backflow of ink17 into the chamber 11 thereby causing a necking and separation of abody of ink 18 which has a continuing momentum and continues towards theoutput media, such as paper, for printing thereof. Subsequently, theactuator 14 returns to its quiescent position and surface tensioneffects result in a refilling of the nozzle chamber 11 via ink supplychannel 13 as a consequence of surface tension effects on the meniscus15. In time, the arrangement returns to that depicted in FIG. 1.

Turning now to FIGS. 4 and 5, there is illustrated the structure of asingle nozzle chamber 10 in more detail. FIG. 4 illustrates partly insection with FIG. 5 showing a corresponding exploded perspective. Inkjet nozzles can be formed, many print heads at a time, on a selectedwafer base 12 utilising standard semiconductor processing techniques inaddition to micro machining and micro fabrication process technology anda full familiarity with these technologies is hereinafter assumed.

On top of the silicon wafer layer 12 is formed a CMOS layer 20. The CMOSlayer 20 can, in accordance with standard techniques, includemulti-level metal layers sandwiched between oxide layers and preferablyat least a two level metal process is utilised. In order to reduce thenumber of necessary processing steps, the masks utilised include areaswhich provide for a build up of an aluminum barrier 21 which can beconstructed from a first 22 and second 23 level aluminum layer.Additionally, aluminum portions eg. 24 are provided for providingelectrical contacts to a subsequent heater layer. The aluminum barrierportion 21 is important in providing an effective barrier to thepossible subsequent etching of the oxide within the CMOS layer 20 when asacrificial etchant is utilised in the construction of a nozzle chamber10 with the etchable material preferably being glass layers.

On top of the CMOS layer 20 is formed a nitride passivation layer 26which is formed to protect the lower CMOS layers from sacrificialetchants and ink erosion. Above the nitride layer 26 there is formed agap 28 in which an air bubble forms during operation. The gap 28 can beconstructed by a means of laying down a sacrificial layer andsubsequently etching the gap as will be explained hereinafter.

On top of the air gap 28 is constructed a polytetrafluoroethylene (PTFE)heater layer 29 which really comprises two PTFE layers that sandwich agold serpentine heater layer 30. The gold heater 30 is constructed in aserpentine form to allow it to expand on heating. The heater layer 30and PTFE layer 29 together comprise the thermal actuator 14 of FIG. 1.

The outer PTFE layer 29 has an extremely high coefficient of thermalexpansion (approximately 770×10⁻⁶, or around 380 times that of silicon).The PTFE layer 29 is also normally highly hydrophobic which results inan air bubble being formed under the actuator in the region 28 due toout-gassing etc. The top PTFE surface layer is treated so as to make ithydrophilic in addition to those areas around ink supply channel 13.This can be achieved with a plasma etch in an ammonia atmosphere. Theheater layer 30 is also formed within the lower portion of the PTFElayer.

The heater layer 30 is connected at ends eg. 31 to the lower CMOS drivelayer 20 which contains the drive circuitry (not shown). For thepurposes of actuation, a current is passed through the gold heaterelement 30 which heats the bottom surface of the actuator 14. The bottomsurface of the actuator 14, in contact with air bubble 28, remainsheated while any top surface heating is carried away by the exposure ofthe top surface of the actuator 14 to the ink within the chamber 32.Hence, the bottom PTFE layer expands more rapidly resulting in a generalrapid bending upwards of actuator 14 (as illustrated in FIG. 2) whichconsequentially causes the ejection of ink from ink ejection port 35.

The actuator 14 can be deactivated by turning off the current to theheater element 30. This results in a return of the actuator 14 to itsrest position.

A nozzle plate comprising side wall portions 33 and top portion 34 isformed on top of the actuator. The nozzle plate can be formed via a dualdamascene process utilising a sacrificial layer. The top portion 34 isetched to have nozzle ink ejection hole 35 in addition to a series ofetchant holes eg. 36 which are of a relatively small diameter and allowfor effective etching of lower sacrificial layers when utilising asacrificial etchant. The etchant holes 36 are made small enough suchthat surface tension effects restrict the possibilities of ink beingejected from the chamber 32 via the etchant holes 36 rather than thenozzle hole 35.

Turning now to FIGS. 6-15, there are set out the various steps involvedin the construction of an array of ink jet nozzles:

1. Turning initially to FIG. 6, the starting position comprises asilicon wafer 12 including a CMOS layer 20 which is passivated by thenitride layer 26 and surface finished with a chemical-mechanicalplanarisation process.

2. The nitride layer 26 is masked and etched as illustrated in FIG. 7 soas to define portions of the nozzle chamber 32 and areas forinterconnection between any subsequent heater layer and a lower CMOSlayer.

3. Next, a sacrificial oxide layer 40 is deposited, masked and etched asindicated in FIG. 8 with the oxide layer being etched in those areaswhere a subsequent heater layer electronically contacts the lowerlayers.

4. As illustrated in FIG. 9, next a 1 micron thick layer of PTFE 41 isthen deposited and firstly masked and etched for the heater contacts tothe lower CMOS layer and secondly masked and etched for the heatershape.

5. Next, as illustrated in FIG. 10, the gold heater layer 30, 31 isdeposited. Due to the fact that it is difficult to etch gold, the layercan be conformally deposited and portions of the layer subsequentlyremoved utilising chemical mechanical planarisation so as to leave thoseportions associated with the heater element. The processing steps 4 and5 basically generate a dual damascene.

6. Next, a top PTFE layer 42 is deposited and masked and etched down tothe sacrificial layer as illustrated in FIG. 11 so as to define theheater shape. Subsequently, the surface of the PTFE layer 42 is plasmaprocessed so as to make it hydrophilic. Suitable processing canincluding plasma damage in an ammonia atmosphere. Alternatively, thesurface can be coated with a hydrophilic material.

7. A further sacrificial oxide layer 43 is then deposited and etched asillustrated in FIG. 12 so as to form a structure for a nozzle chamber32. The sacrificial layer 43 is masked and etched in order to define thenozzle chamber walls.

8. Next, as illustrated in FIG. 13, the nozzle chamber is formed byconformally depositing three microns of nitride to form the nitridenozzle plate. A mask nozzle rim is etched to a depth of one micron forthe nozzle rim (the etched depth not being overly time critical).Subsequently, a mask is utilised to etch the nozzle holes 35 in additionto the sacrificial layer etchant holes 36.

9. Next, as illustrated in FIG. 14, a back of the wafer is masked forthe ink channels 13 and plasma etched through the wafer. A suitableplasma etching process can include a deep anisotropic trench etchingsystem such as that available from SDS Systems Limited (See) “AdvancedSilicon Etching Using High Density Plasmas” by J. K. Bhardwaj, H.Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in MicroMachining and Micro Fabrication Process Technology).

10. Next, as illustrated in FIG. 15, the sacrificial layers are etchedaway utilising a sacrificial etchant such as hydrofluoric acid.Subsequently, the portion underneath the actuator which is around theink channel is plasma processed through the back of the wafer to makethat position hydrophilic.

Subsequently, the wafer contains a number of the ink jet printer headsthat can be separated into separate print head chips with each printhead chip bonded into an injection molded ink supply channel. Theelectrical signals to the chips can be tape automated bonded (TAB) tothe print head for subsequent testing. FIG. 16 illustrates a top view ofjet nozzles constructed on a wafer so as to provide for page widthmulticolor output.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet print heads operating in accordance withthe principles taught by the present embodiment can proceed utilizingthe following steps:

1. Using a double sided polished wafer 12, provide complete drivetransistors, data distribution, and timing circuits using a 0.5 micron,one poly, 2 metal CMOS processor 20. This step is shown in FIG. 18. Forclarity, these diagrams may not be to scale, and may not represent across section though any single plane of the nozzle. FIG. 17 is a key torepresentations of various materials in these manufacturing diagrams,and those of other cross referenced ink jet configurations.

2. Deposit 1 micron of low stress nitride 50. This acts as a barrier toprevent ink diffusion through the silicon dioxide of the chip surface.

3. Deposit 3 micron of sacrificial material 51 (e.g. polyimide).

4. Etch the sacrificial layer using 51 Mask 1. This mask defines theactuator anchor point. This step is shown in FIG. 19.

5. Deposit 0.5 microns of PTFE 52.

6. Etch the PTFE, nitride, and CMOS passivation down to second levelmetal using Mask 2. This mask defines the heater vias 31. This step isshown in FIG. 20.

7. Deposit and pattern resist using Mask 3. This mask defines theheater.

8. Deposit 0.5 microns of gold 30 (or other heater material with a lowYoung's modulus) and strip the resist. Steps 7 and 8 form a lift-offprocess. This step is shown in FIG. 21.

9. Deposit 1.5 microns of PTFE 53.

10. Etch the PTFE 53 down to the sacrificial layer 51 using Mask 4. Thismask defines the actuator paddle 14 and the bond pads. This step isshown in FIG. 22.

11. Wafer probe. All electrical connections are complete at this point,and the chips are not yet separated.

12. Plasma process the PTFE 53 to make the top and side surfaces of thepaddle hydrophilic. This allows the nozzle chamber to fill bycapillarity.

13. Deposit 10 microns of sacrificial material 54.

14. Etch the sacrificial material 54 down to nitride 50 using Mask 5.This mask defines the nozzle chamber. This step is shown in FIG. 23.

15. Deposit 3 microns of PECVD glass 55. This step is shown in FIG. 24.

16. Etch to a depth of 1 micron using Mask 6. This mask defines thenozzle rim 56. This step is shown in FIG. 25.

17. Etch down to the sacrificial layer 54 using Mask 7. This maskdefines the nozzle 35 and the sacrificial etch access holes 36. Thisstep is shown in FIG. 26.

18. Back-etch completely through the silicon wafer (with, for example,an ASE Advanced Silicon Etcher from Surface Technology Systems) usingMask 8. This mask defines the ink inlets 13 which are etched through thewafer. The wafer is also diced by this etch. This step is shown in FIG.27.

19. Back-etch the CMOS oxide layers and subsequently deposited nitridelayers 50 and sacrificial layer 51 through to PTFE 53 using theback-etched silicon as a mask.

20. Plasma process the PTFE 53 through the back-etched holes to make thebottom surface of the paddle 14 hydrophilic. This allows the nozzlechamber 11 to fill by capillarity, but maintains a hydrophobic surfaceunderneath the actuator portion of the paddle 14. This hydrophobicsurface causes an air bubble 28 to be trapped under the paddle 14 whenthe nozzle chamber 32 is filled with a water based ink. This bubble 28serves two purposes: to increase the efficiency of the heater bydecreasing thermal conduction away from the heated side of the PTFE, andto reduce the negative pressure on the back of the actuator section ofthe paddle 14.

21. Etch the sacrificial material. The nozzle chambers 32 are cleared,the actuators freed, and the chips are separated by this etch. This stepis shown in FIG. 28.

22. Mount the print heads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink 57 to the ink inlets at the back of the wafer.

23. Connect the print heads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

24. Hydrophobize the front surface of the print heads.

25. Fill the completed print heads with ink 57 and test them. A fillednozzle is shown in FIG. 29.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiments without departing from the spirit orscope of the invention as broadly described. The present embodimentsare, therefore, to be considered in all respects to be illustrative andnot restrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing system including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters high speed pagewidth printers, notebook computers with in-builtpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic“minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per print head, but is a majorimpediment to the fabrication of pagewidth print heads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table above under the heading CrossReferences to Related Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems

For ease of manufacture using standard process equipment, the print headis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the print head is 100mm long, with a width which depends upon the ink jet type. The smallestprint head designed is IJ38, which is 0.35 mm wide, giving a chip areaof 35 square mm. The print heads each contain 19,200 nozzles plus dataand control circuitry.

Ink is supplied to the back of the print head by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprint head is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 which matches the docket numbers in the table under the headingCross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet print heads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, a printer may be listed more than once in a table, where itshares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

Description Advantages Disadvantages Examples ACTUATOR MECHANISM(APPLIED ONLY TO SELECTED INK DROPS) Thermal An electrothermal Largeforce High power Canon Bubblejet bubble heater heats the ink togenerated Ink carrier limited to 1979 Endo et al GB above boiling point,Simple construction water patent 2,007,162 transferring significant Nomoving parts Low efficiency Xerox heater-in-pit heat to the aqueous Fastoperation High temperatures 1990 Hawkins. et al ink. A bubble Small chiparea required U.S. Pat. No. 4,899,181 nucleates and quickly required foractuator High mechanical Hewlett-Packard TIJ forms, expelling the stress1982 Vaught et al ink. Unusual materials U.S. Pat. No. 4,490,728 Theefficiency of the required process is low, with Large drive typicallyless than transistors 0.05% of the electrical Cavitation causes energybeing actuator failure transformed into Kogation reduces kinetic energyof the bubble formation drop. Large print beads are difficult tofabricate Piezo- A piezoelectric crystal Low power Very large area Kyseret al U.S. Pat. No. electric such as lead consumption required foractuator 3,946,398 lanthanum zirconate Many ink types can difficult tointegrate Zoltan U.S. Pat. No. (PZT) is electrically be used withelectronics 3,683,212 activated, and either Fast operation High voltagedrive 1973 Stemme U.S. Pat. No. expands, shears, or High efficiencytransistors required 3,747,120 bends to apply Full pagewidth print EpsonStylus pressure to the ink, heads impractical Tektronix ejecting drops.due to actuator size IJ04 Requires electrical poling in high fieldstrengths during manufacture Electro- An electric field is Low power Lowmaximum Seiko Epson, Usui strictive used to activate consumption strain(approx. et all JP 253401/96 electrostriction in Many ink types can0.01%) IJ04 relaxor materials such be used Large area required as leadlanthanum Low thermal for actuator due to zirconate titanate expansionlow strain (PLZT) or lead Electric field Response speed is magnesinmniobate strength required marginal (˜10 μs) (PMN). (approx. 3.5 V/μm)High voltage drive can be generated transistors required withoutdifficulty Full pagewidth print Does not require heads impracticaielectrical poling due to actuator size Ferro- An electric field is Lowpower Difficult to integrate IJ04 electric used to induce a phaseconsumption with electronics transition hetween the Many ink types canUnusual materials antiferroelectric (AFE) be used such as PLZSnT are andferroelectric (FE) Fast operation required phase. Perovskite (<1 μs)Actuators require a materials such as tin Relatively high large areamodified lead Iongitudinal strain lanthanum zirconate High efficiencytitanate (PLZSnT) Electric field exhibit large strains of strength ofaround 3 up to 1% associated V/μm can be readily with the AFE to FEprovided phase transition. Electro- Conductive plates are Low powerDifficult to operate IJ02, IJ04 static separated by a consumptionelectrostatic devices plates compressible or fluid Many ink types can inan aqueous dielectric (usually air). be used environment Uponapplication of a Fast operation The electrostatic voltage, the platesactuator will attract each other and normally need to be displace ink,causing separated from the drop ejection. The ink conductive plates mayVery large area be in a comb or required to achieve honeycomb structure,high forces or stacked to increase High voltage drive the surface areaand transistors may be therefore the force. required Full pagewidthprint heads are not competitive due to actuator size Electro- A strongelectric field Low current High voltage 1989 Saito et al, static pull isapplied to the ink, consumption required U.S. Pat. No. 4,799,068 on inkwhereupon Low temperature May be damaged by 1989 Miura et al,electrostatic attraction sparks due to air U.S. Pat. No. 4,810,954accelerates the ink breakdown Tone-jet towards the print Required fieldmedium. strength increases as the drop size decreases High voltage drivetransistors required Electrostatic field attracts dust Permanent Anelectromagnet Low power Complex fabrication IJ07, IJ10 magnet directlyattracts a consumption Permanent magnetic electro- permanent magnet,Many ink types can material such as magnetic displacing ink and he usedNeodymium Iron causing drop ejection. Fast operation Boron (NdFeB) Rareearth magnets High efficiency required. with a field strength Easyextension from High local currents around 1 Tesla can be single nozzlesto required used. Examples are: pagewidth print Copper metalizationSamarium Cobalt heads should be used for (SaCo) and magnetic longmaterials in the electromigration neodymium iron boron lifetime and lowfamily (NdFeB, resistivity NdDyFeBNb, Pigmented inks are NdDyFeB, etc)usually infeasibie Operating temperature limited to the Curietemperature (around 540 K.) Soft A solenoid induced a Low power Complexfabrication IJ01, IJ05, IJ08, magnetic magnetic field in a softconsumption Materials not IJ10, IJ12, IJ14, core magnetic core or yokeMany ink types can usually present in a IJ15, IJ17 electro- fabricatedfrom a be used CMOS fab such as magnetic ferrous material such Fastoperation NiFe, CoNiFe, or as electroplated iron High efficiency CoFeare required alloys such as CoNiFe Easy extension from High localcurrents [1], CoFe, or NiFe single nozzles to required alloys.Typically, the pagewidth print Copper metalization soft magneticmaterial heads should be used for is in two parts, which long arenormally held electromigration apart by a spring. lifetime and low Whenthe solenoid is resistivity actuated, the two parts Electroplating isattract, displacing the required ink. High saturation flux density isrequired (2.0-2.1 Tis achievable with CoNiFe [1]) Lorenz The Lorenzforce Low power Force acts as a IJ06, JJ11, IJ13, force acting on acurrent consumption twisting motion IJ16 carrying wire in a Many inktypes can Typically, only a magnetic field is be used quarter of theutilized. Fast operation solenoid length This allows the High efficiencyprovides force in a magnetic field to be Easy extension from usefuldirection supplied externally to single nozzles to High local currentsthe print head, for pagewidth print required example with rare headsCopper metalization earth permanent should be used for magnets. longOnly the current electromigration carrying wire need be lifetime and lowfabricated on the print- resistivity head, simplifying Pigmented inksare materials usually infeasible requirements. Magneto- The actuatoruses the Many ink types can Force acts as a Fischenbeck, U.S. Pat. No.striction giant magnetostrictive be used twisting motion 4,032,929effect of materials Fast operation Unusual materials IJ25 such asTerfenol-D (an Easy extension from such as Terfenol-D alloy of terbium,single nozzles to are required dysprosium and iron pagewidth print Highlocal currents developed at the Naval heads required OrdnanceLaboratory, High force is Copper metalization hence Ter-Fe-NOL).available should be used for For best efficiency, the long actuatorshould be pre- electromigration stressed to approx. 8 lifetime and lowMPa. resistivity Pre-stressing may be required Surface Ink underpositive Low power Requires Silverbrook, EP tension pressure is held ina consumption supplementaay force 0771 658 A2 and reduction nozzle bysufface Simple construction to effect drop related patent tension. Thesurface No unusual separation applications tension of the ink ismaterials required in Requires special ink reduced below the fabricationsurfactants bubble threshold, High efficiency Speed may be causing theink to Easy extension from limited by surfactant egress from the singlenozzles to properties nozzle. pagewidth print heads Viscosity The inkviscosity is Simple construction Requires Silverbrook, EP reductionlocally reduced to No unusual supplementary force 0771 658 A2 and selectwhich drops are materials required in to effect drop related patent tobe ejected. A fabrication separation applications viscosity reductioncan Easy extension from Requires special ink be achieved single nozzlesto viscosity properties electrothermally with pagewidth print High speedis most inks, but special heads difficult to achieve inks can beengineered Requires oscillating for a 100:1 viscosity ink pressurereduction. A high temperature difference (typically 80 degrees) isrequired Acoustic An acoustic wave is Can operate without Complex drive1993 Hadimioglu et generated and a nozzle plate circuitry al, EUP550,192 focussed upon the Complex fabrication 1993 Elrod et al, dropejection region. Low efficiency EUP 572,220 Poor control of dropposition Poor control of drop volume Thermo- An actuator which Low powerEfficient aqueous IJ03, IJ09, IJ17, elastic relies upon differentialconsumption operation requires a IJ18, IJ19, IJ20, bend thermalexpansion Many ink types can thermal insulator on IJ21, IJ22, IJ23,actuator upon Joule heating is be. used the hot side IJ24, IJ27, IJ28,used. Simple planar Corrosion IJ29, IJ30, IJ31, fabrication preventioncan be IJ32, IJ33, IJ34, Small chip area difficult IJ35, IJ36, IJ37,required for each Pigmented inks may IJ38 ,IJ39, IJ40, actuator beinfeasible, as IJ41 Fast operation pigment particles High efficiency mayjam the bend CMOS compatible actuator voltages and currents StandardMEMS processes can be used Easy extension from single nozzles topagewidth print heads High CTE A material with a very High force can beRequires special IJ09, IJ17, IJ18, thermo- high coefficient of generatedmaterial (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermal expansion Threemethods of Requires a PTFE IJ23, IJ24, IJ27, actuator (CTE) such as.PTFE deposition are deposition process, IJ28, IJ29, IJ30,polytetrafluoroethylene under development: which is not yet IJ31, IJ42,IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTEmaterials deposition (CVD), fabs are usually non- spin coating, and PTFEdeposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a candidate with high conductive material isfor low dielectric temperature (above incorporated. A 50 μm constantinsulation 350° C.) processing long PTFE bend in ULSI Pigmented inks mayactuator with Very low power be infeasible, as polysilicon heater andconsumption pigment particles 15 mW power input Many ink types can mayjam the bend can provide 180 μN be used actuator force and 10 μm Simpleplanar deflection. Actuator fabrication motions include: Small chip areaBend required for each Push actuator Buckle Fast operation Rotate Highefficiency CMOS compatible voltages and currents Easy extension fromsingle nozzles to pagewidth print heads Conduct- A polymer with a highHigh force can be Requires special IJ24 ive coefficient of thermalgenerated materials polymer expansion (such as Very low powerdevelopment (High thermo- PTFE) is doped with consumption CTE conductiveelastic conducting substances Many ink types can polymer) actuator toincrease its be used Requires a PThE conductivity to about 3 Simpleplanar deposition process, orders of magnitude fabrication which is notyet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS compatible temperature (aboveconducting dopants voltages and 350° C.) processing include: currentsEvaporation and Carbon nanotubes Easy extension from CVD depositionMetal fibers single nozzles to techniques cannot Conductive polymerspagewidth print be used such as doped heads Pigmented inks maypolythiophene be infeasible, as Carbon granules pigment particles mayjam the bend actuator Shape A shape memory alloy High force is Fatiguelimits IJ26 memory such as TiNi (also available (stresses maximum numberalloy known as Nitinol - of hundreds of MPa) of cycles Nickel Titaniumalloy Large strain is Low strain (1%) is developed at the Navalavailable (more than required to extend Ordnance Laboratory) 3%) fatigueresistance is thermally switched High corrosion Cycle rate limitedbetween its weak resistance by heat removal martensitic state and Simpleconstruction Requires unusual its high stiffness Easy extension frommaterials (TiNi) austenic state. The single nozzles to The latent heatof shape of the actuator pagewidth print transformation must in itsmartensitic state heads be provided is deformed relative to Low voltageHigh current the austenic shape. operation operation The shape changeRequires pre- causes ejection of a stressing to distort drop. themartensitic state Linear Linear magnetic Linear Magnetic Requiresunusual IJ12 Magnetic actuators include the actuators can besemiconductor Actuator Linear Induction constructed with materials suchas Actuator (LIA), Linear high thrust, long soft magnetic alloysPermanent Magnet travel, and high (e.g. CoNiFe) Synchronous Actuatorefficiency using Some varieties also (LPMSA), Linear planar requirepermanent Reluctance semiconductor magnetic materials SynchronousActuator fabrication such as Neodymium (LRSA), Linear techniques ironboron (NdFeB) Switched Reluctance Long actuator travel Requires complexActuator (LSRA), and is available multi-phase drive the Linear StepperMedium force is circuitry Actuator (LSA). available High current Lowvoltage operation operation BASIC OPERATION MODE Actuator This is thesimplest Simple operation Drop repetition rate Thermal ink jet directlymode of operation: the No external fields is usually limited toPiezoetectri.#c imk jet pushes ink actuator directly required around 10kHz. IJ01, IJ02, IJ03, supplies sufficient Satellite drops can However,this is not IJ04, IJ05, IJ06, kinetic energy to expel be avoided if dropfundamental to the IJ07, IJ09, IJ11, the drop. The drop velocity is lessthan method, but is IJ12, IJ14, IJ16, must have a sufficient 4 mlsrelated to the refill IJ20, IJ22, IJ23, velocity to overcome Can beefficient, method normally IJ24, IJ25, IJ26, the surface tension.depending upon the used IJ27, IJ28, IJ29, actuator used All of the dropIJ30, IJ31, IJ32, kinetic energy must IJ33, IJ34, IJ35, be provided bythe IJ36, IJ37, IJ38, actuator IJ39, IJ40, IJ41, Satellite drops IJ42,IJ43, IJ44 usually form if drop velocity is greater than 4.5 mlsProximity The drops to be Very simple print Requires close Silverbrook,EP printed are selected by head fabrication can proximity between 0771658 A2 and some manner (e.g. be used the print head and related patentthermally induced The drop selection the print media or applicationssurface tension means does not need transfer roller reduction of toprovide ffie May require two pressurized ink). energy required to printheads printing Selected drops are separate the drop alternate rows ofthe separated from the ink from the nozzle image in the nozzle byMonolithic color contact with the print print heads are medium or atransfer difficult roller. Electro- The drops to be Very simple printRequires very high Silverbrook, EP static pull printed are selected byhead fabrication can electrostatic field 0771 658 A2 and on ink somemanner (e.g. be used Electrostatic field related patent thermallyinduced The drop selection for small nozzle applications surface tensionmeans does not need sizes is above air Tone-Jet reduction of to providethe breakdown pressurized ink). energy required to Electrostatic fieldSelected drops are separate the drop may attract dust separated from theink from the nozzle in the nozzle by a strong electric field. MagneticThe drops to be Very simple print Requires magnetic Silverbrook, EP pullon ink printed are selected by head fabrication can ink 0771 658 A2 andsome manner (e.g. be used Ink colors other than related patent thermallyinduced The drop selection black are difficult applications surfacetension means does not need Requires very high reduction of to providethe magnetic fields (pressurized ink). energy required to Selected dropsare separate the drop separated from the ink from the nozzle in thenozzle by a strong magnetic field acting on the magnetic ink. ShutterThe actuator moves a High speed (>50 Moving parts are IJIJ, IJ17, IJ21shutter to block ink kHz) operation can required flow to the nozzle. Thebe achieved due to Reqwres ink ink pressure is pulsed reduced refilltime pressure modulator at a multiple of the Drop timing can be Frictionand wear drop ejection very accurate must be considered frequency. Theactuator energy Stiction is possible can be very low Shuttered Theactuator moves a Actuators with Moving parts are IJ08, IJ15, IJ18, grillshutter to block ink small travel can be required IJ19 flow through agrill to used Requires ink the nozzle. The shutter Actuators withpressure modulator movement need only small force can be Friction andwear be equal to the width used must be considered of the grill holes.High speed (>50 Stiction is possible kHz) operation can be achievedPulsed A pulsed magnetic Extremely low Requires an external IJ10magnetic field attracts an ‘ink energy operation is pulsed magnetic pullon ink pusher’ at the drop possible field pusher ejection frequency. AnNo heat dissipation Requires special actuator controls a problemsmaterials for both catch, which prevents the actuator and the the inkpusher from ink pusher moving when a drop is Complex not to be ejected.construction AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) None Theactuator directly Simplicity of Drop ejection Most ink jets, fires theink drop, and construction energy must be including there is no externalSimplicity of supplied by piezoelectric and field or other operationindividual nozzle thermal bubble. mechanism required. Small physicalsize actuator I301, IJ02, IJ03, IJ04, IJ05, IJ07, IJ09, IJ11, IJ12,IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31,IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43,IJ44 Oscillating The ink pressure Oscillating ink Requires externalSilverbrook, EP ink oscillates, providing pressure can proyide inkpressure 0771 658 A2 and pressure much of the drop a reflll pulse,oscillator related patent (including ejection energy. The allowinghigher Ink pressure phase applications acoustic actuator selects whichoperating speed and amplitude must IJ08, IJ13, IJ15, stimul- drops areto be fired The actuators may be carefully IJ17, IJ18, IJ19, ation) byselectively operate with much controlled IJ21 blocking or enabling lowerenergy Acoustic reflections nozzles. The ink Acoustic lenses can in theink chamber pressure oscillation be used to focus.the must be designedmay be achieved by sound on the for vibrating the print nozzles head, orpreferably by an actuator in the ink supply. Media The print head is Lowpower Precision assembly Silverbrook, EP proximity placed in close Highaccuracy required 0771 658 A2 and proximity to the print Simple printhead Paper fibers may related patent medium. Selected construction causeproblems applications drops protrude from Cannot print on the print headfurther rough substrates than unselected drops, and contact the printmedium. The drop soaks into the medium fast enough to cause dropseparation. Transfer Drops are printed to a High accuracy BulkySilverbrook, EP roller transfer roller instead Wide range of printExpensive 0771 658 A2 and of straight to the print substrates can beComplex related patent medium. A transfer used construction applicationsroller can also be used Ink can be dried on Tektronix hot melt forproximity drop the transfer roller piezoelectric ink jet separation. Anyof the IJ series Electro- An electric field is Low power Field strengthSilverbrook, EP static used to accelerate Simple print head required for0771 658 A2 and selected drops towards construction separation of smallrelated patent the print medium. drops is near or applications above airTone-Jet breakdown Direct A magnetic field is Low power Requiresmagnetic Silverbrook, EP magnetic used to accelerate Simple print headink 0771 658 A2 and field selected drops of construction Requires strongrelated patent magnetic ink towards magnetic field applications theprint medium. Cross The print head is Does not require Requires externalIJ06, IJ16 magnetic placed in a constant magnetic materials magnet fieldmagnetic field. The to be integrated in Current densities Lorenz forcein a the print head may be high, current carrying wire manufacturingresulting in is used to move the process. electromigration actuator.problems Pulsed A pulsed magnetic Very low power Complex print head IJ10magnetic field is used to operation is possible construction fieldcyclically attract a Small print head Magnetic materials paddle, whichpushes size required in print on the ink. A small head actuator moves acatch, which selectively prevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many actuatorThermal Bubble Ink mechanical simplicity mechanisms have jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be taken IJ18, IJ19, IJ20, actuator The expansion may be thatthe materials do IJ21, IJ22, IJ23, thermal, piezoelectric, notdelaminate IJ24, IJ27, IJ29, magnetostrictive, or Residual bend IJ30,IJ31, IJ32, other mechanism. The resulting from high IJ33, IJ34, IJ35,bend actuator converts temperature or high IJ36, IJ37, IJ38, a highforce low travel stress during IJ39, IJ42, IJ43, actuator mechanism toformation IJ44 high travel, lower force mechanism. Transient A trilayerbend Very good High stresses are IJ40, IJ41 bend actuator where the twotemperature stability involved actuator outside layers are High speed,as a Care must be taken identical. This cancels new drop can be that thematerials do bend due to ambient fired before heat not delaminatetemperature and dissipates residual stress. The Cancels residualactuator only responds stress of formation to transient heating of oneside or the other. Reverse The actuator loads a Better coupling toFabrication IJ05, IJ11 spring spring. When the the ink complexityactuator is turned off, High stress in the the spring reieases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some piezoelectricstack actuators are stacked. Reduced drive fabrication ink jets This canbe voltage complexity IJ04 appropriate where Increased possibilityactuators require high of short circuits due electric field strength, topinholes such as electrostatic and piezoelectric actuators. MultipleMultiple smaller Increases the force Actuator forces may IJ12, IJ13,IJ18, actuators actuators are used available from an not add linearly,IJ20, IJ22, IJ28, simultaneously to actuator reducing efficiency IJ42,IJ43 move the ink. Each Multiple actuators actuator need provide can bepositioned to only a portion of the control ink flow force required.accurately Linear A linear spring is used Matches low travel Requiresprint head IJ15 Spring to transform a motion actuator with higher areafor the spring with small travel and travel requirements high force intoa Non-contact method longer travel, lower of motion force motion.transformation Coiled A bend actuator is Increases travel Generallyrestricted IJ17, IJ21, IJ34, actuator coiled to provide Reduces chiparea to planar IJ35 greater travel in a Planar implementations reducedchip area. implementations are due to extreme relatively easy tofabrication difficulty fabricate. in other orientations. Flexure A bendactuator has a Simple means of Care must be taken IJ10, IJ19, IJ33 bendsmall region near the increasing travel of not to exceed the actuatorfixture point, which a bend actuator elastic limit in the flexes muchmore flexure area readily than the Stress distribution is remainder ofthe very uneven actuator. The actuator Difficult to flexing iseffectively accurately model converted from an with finite element evencoiling to an analysis angular bend, resulting in greater travel of theactuator tip. Catch The actuator controls a Very low actuator ComplexIJI0 small catch. The catch energy construction either enables or Verysmall actuator Requires external disables movement of size force an inkpusher that is Unsuitable for controlled in a bulk pigmented inksmanner. Gears Gears can be used to Low force, low Moving parts are IJ13increase travel at the travel actuators can required expense ofduration. be used Several actuator Circular gears, rack Can befabricated cycles are required and pinion, ratchets, using standard Morecomplex drive and other gearing surface MEMS electronics methods can beused. processes Complex construction Friction, friction, and wear arepossible Buckle A buckle plate can be Very fast movement Must staywithin S. Hirata et al, “An plate used to change a slow achievableelastic limits of the Ink-jet Head Using actuator into a fast materialsfor long Diaphragm motion. It can also device life Microactuator”,convert a high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, pp 418- into a high travel, Generally high 423.medium force motion. power requirement IJ18, IJ27 Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low travel High stress around IJ32,IJ36, IJ37 used to transform a actuator with higher the fulcrum motionwith small travel requirements travel and high force Fulcrum area has nointo a motion with linear movement, longer travel and and can be usedfor lower force. The lever a fluid seal can also reverse the directionof travel. Rotary The actuator is High mechanical Complex IJ28 impellerconnected to a rotary advantage construction impeller. A small The ratioof force to Unsuitable for angular deflection of travel of the actuatorpigmented inks the actuator results in can be matched to a rotation ofthe the nozzle impeller vanes, which requirements by push the inkagainst varying the number stationary vanes and of impeller vanes out ofthe nozzle. Acoustic A refractive or No moving parts Large area required1993 Hadimioglu et lens diffractive (e.g. zone Only relevant for al, EUP550,192 plate) acoustic lens is acoustic ink jets 1993 Elrod et al, usedto concentrate EUP 572,220 sound waves. Sharp A sharp point is usedSimple construction Difficult to fabricate Tone-jet conductive toconcentrate an using standard VLSI point electrostatic field. processesfor a surface ejecting ink- jet Only relevant for electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the ♦ Simple construction ♦ High energy is ♦ Hewlett-Packardexpansion actuator changes, in the case of typically required to ThermalInk jet pushing the ink in all thermal ink jet achieve volume ♦ CanonBubblejet directions. expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator moves in ♦ Efficient coupling to ♦ High fabrication ♦ IJ01,IJ02, 1J04, normal to a direction normal to ink drops ejected complexitymay be IJ07, IJ11, IJ14 chip the print head surface. normal to therequired to achieve surface The nozzle is typically surfaceperpendicular in the line of motion movement. Parallel to The actuatormoves ♦ Suitable for planar ♦ Fabrication ♦ IJ12, IJ13, IJ15, chipparallel to the print fabrication complexity IJ33, IJ34, IJ35, surfacehead surface. Drop ♦ Friction IJ36 ejection may still be ♦ Stictionnormal to the surface. Membrane An actuator with a ♦ The effective areaof ♦ Fabrication ♦ 1982 Howkins push high force but small the actuatorcomplexity U.S. Pat. No. 4,459,601 area is used to push a becomes the ♦Actuator size stiff membrane that is membrane area ♦ Difficulty of incontact with the ink. integration in a VLSI process Rotary The actuatorcauses ♦ Rotary levers may ♦ Device complexity ♦ IJ05, IJ08, IJ13, therotation of some be used to increase ♦ May have friction at IJ28element, such a grill or travel a pivot point impeller ♦ Small chip arearequirements Bend The actuator bends ♦ A very small change ♦ Requiresthe ♦ 1970 Kyser et al when energized. This in dimensions can actuatorto be made U.S. Pat. No. 3,946,398 may be due to be converted to a fromat least two ♦ 1973 Stemme differential thermal large motion. distinctlayers, or to U.S. Pat. No. 3,747,120 expansion, have a thermal ♦ IJ03,IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24,expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33,IJ34, other form of relative IJ35 dimensional change. Swivel Theactuator swivels ♦ Allows operation ♦ Inefficient coupling ♦ IJ06 arounda central pivot. where the net linear to the ink motion This motion issuitable force on the paddle where there are is zero opposite forces ♦Small chip area applied to opposite requirements sides of the paddle,e.g. Lorenz force. Straighten The actuator is ♦ Can be used with ♦Requires careful ♦ IJ26, IJ32 normally bent, and shape memory balance ofstresses straightens when alloys where the to ensure that the energized.austenic phase is quiescent bend is planar accurate Double The actuatorbends in ♦ One actuator can be ♦ Difficult to make ♦ IJ36, IJ37, IJ38bend one direction when used to power two the drops ejected by oneelement is nozzles. both bend directions energized, and bends ♦ Reducedchip size. identical. the other way when ♦ Not sensitive to ♦ A smallefficiency another element is ambient temperature loss compared toenergized. equivalent single bend actuators. Shear Energizing the ♦ Canincrease the ♦ Not readily ♦ 1985 Fishbeck actuator causes a sheareffective travel of applicable to other U.S. Pat. No. 4,584,590 motionin the actuator piezoelectric actuator material. actuators mechanismsRadial The actuator squeezes ♦ Relatively easy to ♦ High force required♦ 1970 Zoltan con- an ink reservoir, fabricate single ♦ Inefficient U.S.Pat. No. 3,683,212 striction forcing ink from a nozzles from glass ♦Difficult to integrate constricted nozzle. tubing as with VLSImacroscopic processes structures Coil/ A coiled actuator ♦ Easy tofabricate as ♦ Difficult to fabricate ♦ IJ17, IJ21, IJ34, uncoil uncoilsor coils more a planar VLSI for non-planar IJ35 tightly. The motion ofprocess devices the free end of the ♦ Small area required, ♦ Poorout-of-plane actuator ejects the ink. therefore low cost stiffness BowThe actuator bows (or ♦ Can increase the ♦ Maximum travel is ♦ IJ16,IJ18, IJ27 buckles) in the middle speed of travel constrained whenenergized. ♦ Mechanically rigid ♦ High force required Push-Pull Twoactuators control ♦ The structure is ♦ Not readily suitable ♦ IJ18 ashutter. One actuator pinned at both ends, for ink jets which pulls theshutter, and so has a high out-of- directly push the ink the otherpushes it. plane rigidity Curl A set of actuators curl ♦ Good fluid flowto ♦ Design complexity ♦ IJ20, IJ42 inwards inwards to reduce the theregion behind volume of ink that the actuator they enclose. increasesefficiency Curl A set of actuators curl ♦ Relatively simple ♦ Relativelylarge ♦ IJ43 outwards outwards, pressurizing construction chip area inkin a chamber surrounding the actuators, and expelling ink from a nozzlein the chamber. Iris Multiple vanes enclose ♦ High efficiency ♦ Highfabrication ♦ IJ22 a volume of ink. These ♦ Small chip area complexitysimultaneously rotate, ♦ Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates ♦ The actuatorcan be ♦ Large area required ♦ 1993 Hadimioglu et vibration at a highfrequency. physically distant for efficient al, EUP 550,192 from the inkoperation at useful ♦ 1993 Elrod et al, frequencies EUP 572,220 ♦Acoustic coupling and crosstalk ♦ Complex drive circuitry ♦ Poor controlof drop volume and position None In various ink jet ♦ No moving parts ♦Various other ♦ Silverbrook, EP designs the actuator tradeoffs are 0771658 A2 and does not move. required to related patent eliminate movingapplications parts ♦ Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way ♦ Fabrication ♦ Low speed ♦ Thermal inkjet tension that ink jets are simplicity ♦ Surface tension ♦Piezoelectric ink jet refilled. After the ♦ Operational force relatively♦ IJ01-IJ07, IJ10-IJ14, actuator is energized, simplicity small comparedto IJ16, IJ20, IJ22-IJ45 it typically returns actuator force rapidly toits normal ♦ Long refill time position. This rapid usually dominatesreturn sucks in air the total repetition through the nozzle rateopening. The ink surface tension at the nozzle then exerts a small forcerestoring the meniscus to a minimum area. This force refills the nozzle.Shuttered Ink to the nozzle ♦ High speed ♦ Requires common ♦ IJ08, IJ13,IJ15, oscillating chamber is provided at ♦ Low actuator ink pressureIJ17, IJ18, IJ19, ink a pressure that energy, as the oscillator IJ21pressure oscillates at twice the actuator need only ♦ May not besuitable drop ejection open or close the for pigmented inks frequency.When a shutter, instead of drop is to be ejected, ejecting the ink dropthe shutter is opened for 3 half cycles: drop ejection, actuator return,and refill. The shutter is then closed to prevent the nozzle chamberemptying during the next negative pressure cycle. Refill After the main♦ High speed, as the ♦ Requires two ♦ IJ09 actuator actuator has ejecteda nozzle is actively independent drop a second (refill) refilledactuators per nozzle actuator is energized. The refill actuator pushesink into the nozzle chamber. The refill actuator returns slowly, toprevent its return from emptying the chamber again. Positive The ink isheld a slight ♦ High refill rate, ♦ Surface spill must ♦ Silverbrook, EPink positive pressure. therefore a high be prevented 0771 658 A2 andpressure After the ink drop is drop repetition rate ♦ Highly hydrophobicrelated patent ejected, the nozzle is possible print head surfacesapplications chamber fills quickly are required ♦ Alternative for:, assurface tension and IJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20,IJ22-IJ45 operate to refill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel Designsimplicity Restricts refill rate Thermal ink jet channel to the nozzlechamber Operational May result in a Piezoelectric ink jet is made longand simplicity relatively large chip IJ42, IJ43 relatively narrow,Reduces crosstalk area relying on viscous Only partiaily drag to reduceinlet effective back-flow. Positive The ink is under a Drop selectionand Requires a method Silverbrook, EP ink positive pressure, soseparation forces (such as a nozzle 0771 658 A2 and pressure that in thequiescent can be reduced rim or effective related patent state some ofthe ink Fast refill time hydrophobizing, or applications drop alreadyprotrudes both) to prevent Possible operation from the nozzle. floodingof the of the following: This reduces the ejection surface of IJ01-IJ07,IJ09- pressure in the nozzle the print head. IJ12, IJ14, IJ16, chamberwhich is IJ20, IJ22, IJ23- required to eject a IJ34, IJ36-IJ41, certainvolume of ink. IJ44 The reduction in chamber pressure results in areduction in ink pushed out through the iniet. Baffle One or morebaffles The refill rate is not Design complexity HP Thermal Ink Jet areplaced in the inlet as restricted as the May increase Tektronix inkflow. When the long inlet method. fabrication piezoelectric ink jetactuator is energized, Reduces crosstalk complexity (e.g. the rapid inkTektronix hot melt movement creates Piezoelectric print eddies whichrestrict heads). the flow through the inlet. The slower refill processis unrestricted, and does not result in eddies. Flexible In this methodrecently Significantly Not applicable to Canon lIap disclosed by Canon,reduces back-flow most ink jet restricts the expanding actuator foredge-shooter configurations inlet (bubble) pushes on a thermal ink jetIncreased flexibie fiap that devices fabrication restricts the inlet.complexity Inelastic deformation of polymer flap results in creep overextended use Inlet fiIter A filter is located Additional Restrictsrefill rate IJ04, IJ12, IJ24, between the ink inlet advantage of ink Mayresult in IJ27, IJ29, IJ30 and the nozzle filtration complex chamber.The filter Ink filter may be construction has a multitude of fabricatedwith no small holes or slots, additional process restricting ink flow.steps The filter also removes particles which may block the nozzle.Small inlet The ink inlet channel Design simplicity Restricts refillrate IJ02, IJ37, IJ44 compared to the nozzle chamber May result in a tonozzle has a substantially relatively large chip smaller cross sectionarea than that of the nozzle, Only partially resulting in easier inkeffective egress out of the nozzle than out of the inlet. Inlet Asecondary actuator Increases speed of Requires separate IJ09 shuttercontrols the position of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowproblem Requires careful IJ01, IJ03, IJ05, located problem of inletback- is eliminated design to minimize IJ06, IJ07, IJ10, behind the flowby arranging the the negative IJ11, IJ14, IJ16, ink- ink-pushing surfaceof pressure behind the IJ22, IJ23, IJ25, pushing the actuator betweenpaddle IJ28, IJ31, IJ32, surface the inlet and the IJ33, IJ34, IJ35,nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off so that the motion of achieved the inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to ink Silverbrook, EPactuator of ink jet, there is no problem is back-flow on 0771 658 A2 anddoes not expansion or eliminated actuation related patent result inmovement of an applications ink back- actuator which may Valve-jet flowcause ink back-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are ♦ No added ♦ May not be ♦ Most ink jetsystems nozzle fired periodically, complexity on the sufficient to ♦IJ01, IJ02, IJ03, firing before the ink has a print head displace driedink IJ04, IJ05, IJ06, chance to dry. When IJ07, IJ09, IJ10, not in usethe nozzles IJ11, IJ12, IJ14, are sealed (capped) IJ16, IJ20, IJ22,against air. IJ23, IJ24, IJ25, The nozzle firing is IJ26, IJ27, IJ28,usually performed IJ29, IJ30, IJ31, during a special IJ32, IJ33, IJ34,clearing cycle, after IJ36, IJ37, IJ38, first moving the print IJ39,IJ40, IJ41, head to a cleaning IJ42, IJ43, IJ44, station. IJ45 Extra Insystems which heat ♦ Can be highly ♦ Requires higher ♦ Silverbrook, EPpower to the ink, but do not boil effective if the drive voltage for0771 658 A2 and ink heater it under normal heater is adjacent toclearing related patent situations, nozzle the nozzle ♦ May requirelarger applications clearing can be drive transistors achieved by over-powering the heater and boiling ink at the nozzle. Rapid The actuator isfired in ♦ Does not require ♦ Effectiveness ♦ May be used with: success-rapid succession. In extra drive circuits depends IJ01, IJ02, IJ03, ionof some configurations, on the print head substantially upon IJ04, IJ05,IJ06, actuator this may cause heat ♦ Can be readily the configuration ofIJ07, IJ09, IJ10, pulses build-up at the nozzle controlled and the inkjet nozzle IJ11, IJ14, IJ16, which boils the ink, initiated by digitalIJ20, IJ22, IJ23, clearing the nozzle. In logic IJ24, IJ25, IJ27, othersituations, it may IJ28, IJ29, IJ30, cause sufficient IJ31, IJ32, IJ33,vibrations to dislodge IJ34, IJ36, IJ37, clogged nozzles. IJ38, IJ39,IJ40, IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is ♦ A simplesolution ♦ Not suitable where ♦ May be used with: power to not normallydriven to where applicable there is a hard limit IJ03, IJ09, IJ16, inkthe limit of its motion, to actuator IJ20, IJ23, IJ24, pushing nozzleclearing may be movement IJ25, IJ27, IJ29, actuator assisted byproviding IJ30, IJ31, IJ32, an enhanced drive IJ39, IJ40, IJ41, signalto the actuator. IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is ♦A high nozzle ♦ High ♦ IJ08, IJ13, IJ15, resonance applied to the inkclearing capability implementation cost IJ17, IJ18, IJ19, chamber. Thiswave is can be achieved if system does not IJ21 of an appropriate ♦ Maybe already include an amplitude and implemented at very acousticactuator frequency to cause low cost in systems sufficient force at thewhich already nozzle to clear include acoustic blockages. This isactuators easiest to achieve if the ultrasonic wave is at a resonantfrequency of the ink cavity. Nozzle A microfabricated ♦ Can clearseverely ♦ Accurate ♦ Silverbrook, EP clearing plate is pushed againstclogged nozzles mechanical 0771 658 A2 and plate the nozzles. The platealignment is related patent has a post for every required applicationsnozzle. A post moves ♦ Moving parts are through each nozzle, requireddisplacing dried ink. ♦ There is risk of damage to the nozzles ♦Accurate fabrication is required Ink The pressure of the ink ♦ May beeffective ♦ Requires pressure ♦ May be used with pressure is temporarilywhere other pump or other all IJ series ink jets pulse increased so thatink methods cannot be pressure actuator streams from all of the used ♦Expensive nozzles. This may be ♦ Wasteful of ink used in conjunctionwith actuator energizing. Print head A flexible ‘blade’ is ♦ Effectivefor planar ♦ Difficult to use if ♦ Many ink jet wiper wiped across theprint print head surfaces print head surface is systems head surface.The ♦ Low cost non-planar or very blade is usually fragile fabricatedfrom a ♦ Requires flexible polymer, e.g. mechanical parts rubber orsynthetic ♦ Blade can wear out elastomer. in high volume print systemsSeparate A separate heater is ♦ Can be effective ♦ Fabrication ♦ Can beused with ink boiling provided at the nozzle where other nozzlecomplexity many IJ series ink heater although the normal clearingmethods jets drop e-ection cannot be used mechanism does not ♦ Can beimplemented require it. The heaters at no additional cost do not requirein some ink jet individual drive configurations circuits, as manynozzles can be cleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages ExamplesElectro- A nozzle plate is ♦ Fabrication ♦ High temperatures ♦ HewlettPackard formed separately fabricated simplicity and pressures areThermal Ink jet nickel from electroformed required to bond nickel, andbonded to nozzle plate the print head chip. ♦ Minimum thicknessconstraints ♦ Differential thermal expansion Laser Individual nozzle ♦No masks required ♦ Each hole must be ♦ Canon Bubblejet ablated or holesare ablated by an ♦ Can be quite fast individually formed ♦ 1988 Sercelet al., drilled intense UV laser in a ♦ Some control over ♦ Specialequipment SPIE, Vol. 998 polymer nozzle plate, which is nozzle profileis required Excimer Beam typically a polymer possible ♦ Slow where thereApplications, pp. such as polyimide or ♦ Equipment required are manythousands 76-83 polysulphone is relatively low cost of nozzles per print♦ 1993 Watanabe et al., head U.S. Pat. No. 5,208,604 ♦ May produce thinburrs at exit holes Silicon A separate nozzle ♦ High accuracy is ♦ Twopart ♦ K. Bean, IEEE micro- plate is attainable constructionTransactions on machined micromachined from ♦ High cost ElectronDevices, single crystal silicon, ♦ Requires precision Vol. ED-25, No.10, and bonded to the alignment 1978, pp 1185-1195 print head wafer. ♦Nozzles may be ♦ Xerox 1990 clogged by adhesive Hawkins et al., U.S.Pat. No. 4,899,181 Glass Fine glass capillaries ♦ No expensive ♦ Verysmall nozzle ♦ 1970 Zoltan capillaries are drawn from glass equipmentrequired sizes are difficult to U.S. Pat. No. 3,683,212 tubing. Thismethod ♦ Simple to make form has been used for single nozzles ♦ Notsuited for mass making individual production nozzles, but is difficultto use for bulk manufacturing of print heads with thousands of nozzles.Monolithic, The nozzle plate is ♦ High accuracy (<1 ♦ Requiressacrificial ♦ Silverbrook, EP surface deposited as a layer μm) layerunder the 0771 658 A2 and micro- using standard VLSI ♦ Monolithic nozzleplate to form related patent machined deposition techniques. ♦ Low costthe nozzle chamber applications using VLSI Nozzles are etched in ♦Existing processes ♦ Surface may be ♦ IJ01, IJ02, IJ04, litho- thenozzle plate using can be used fragile to the touch IJ11, IJ12, IJ17,graphic VLSI lithography and IJ18, IJ20, IJ22, processes etching. IJ24,IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39,IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a ♦ Highaccuracy (<1 ♦ Requires long etch ♦ IJ03, IJ05, IJ06, etched buried etchstop in the μm) times IJ07, IJ08, IJ09, through wafer. Nozzle ♦Monolithic ♦ Requires a support IJ10, IJ13, IJ14, substrate chambers areetched in ♦ Low cost wafer IJ15, IJ16, IJ19, the front of the wafer, ♦No differential IJ21, IJ23, IJ25, and the wafer is expansion IJ26thinned from the back side. Nozzles are then etched in the etch stoplayer. No nozzle Various methods have ♦ No nozzles to ♦ Difficult tocontrol ♦ Ricoh 1995 Sekiya et al plate been tried to eliminate becomeclogged drop position U.S. Pat. No. 5,412,413 the nozzles entirely, toaccurately ♦ 1993 Hadimioglu et prevent nozzle ♦ Crosstalk problems alEUP 550,192 clogging. These ♦ 1993 Elrod et al include thermal bubbleEUP 572,220 mechanisms and acoustic lens mechanisms Trough Each dropejector has ♦ Reduced ♦ Drop firing ♦ IJ35 a trough throughmanufacturing direction is sensitive which a paddle moves. complexity towicking. There is no nozzle ♦ Monolithic plate. Nozzle slit Theelimination of ♦ No nozzles to ♦ Difficult to control ♦ 1989 Saito et alinstead of nozzle holes and become clogged drop position U.S. Pat. No.4,799,068 individual replacement by a slit accurately nozzlesencompassing many ♦ Crosstalk problems actuator positions reduces nozzleclogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesEdge Ink flow is along the ♦ Simple construction ♦ Nozzles limited to ♦Canon Bubblejet (‘edge surface of the chip, ♦ No silicon etching edge1979 Endo et al GB shooter’) and ink drops are required ♦ Highresolution is patent 2,007,162 ejected from the chip ♦ Good heat sinkingdifficult ♦ Xerox heater-in-pit edge. via substrate ♦ Fast colorprinting 1990 Hawkins et al ♦ Mechanically strong requires one printU.S. Pat. No. 4,899,181 ♦ Ease of chip head per color ♦ Tone-jet handingSurface Ink flow is along the ♦ No bulk silicon ♦ Maximum ink flow ♦Hewlett-Packard TIJ (‘roof surface of the chip, etching required isseverely restricted 1982 Vaught et al shooter’) and ink drops are ♦Silicon can make an U.S. Pat. No. 4,490,728 ejected from the chipeffective heat sink ♦ IJ02, IJ11, IJ12, surface, normal to the ♦Mechanical strength IJ20, IJ22 plane of the chip. Through Ink flow isthrough the ♦ High ink flow ♦ Requires bulk ♦ Silverbrook, EP chip,chip, and ink drops are ♦ Suitable for silicon etching 0771 658 A2 andforward ejected from the front pagewidth print related patent (‘upsurface of the chip. heads applications shooter’) ♦ High nozzle packing♦ IJ04, IJ17, IJ18, density therefore IJ24, IJ27-IJ45 low manufacturingcost Through Ink flow is through the ♦ High ink flow ♦ Requires wafer ♦IJ01, IJ03, IJ05, chip, chip, and ink drops are ♦ Suitable for thinningIJ06, IJ07, IJ08, reverse ejected from the rear pagewidth print ♦Requires special IJ09, IJ10, IJ13, (‘down surface of the chip. headshandling during IJ14, IJ15, IJ16, shooter’) ♦ High nozzle packingmanufacture IJ19, IJ21, IJ23, density therefore IJ25, IJ26 lowmanufacturing cost Through Ink flow is through the ♦ Suitable for ♦Pagewidth print ♦ Epson Stylus actuator actuator, which is notpiezoelectric print heads require ♦ Tektronix hot melt fabricated aspart of heads several thousand piezoelectric ink jets the same substrateas connections to drive the drive transistors. circuits ♦ Cannot bemanufactured in standard CMOS fabs ♦ Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Waterbased ink which ♦ Environmentally ♦ Slow drying ♦ Most existing ink dyetypically contains: friendly ♦ Corrosive jets water, dye, surfactant, ♦No odor ♦ Bleeds on paper ♦ All IJ series ink jets humectant, and ♦ Maystrikethrough ♦ Silverbrook, EP biocide. ♦ Cockles paper 0771 658 A2 andModern ink dyes have related patent high water-fastness, applicationslight fastness Aqueous, Water based ink which ♦ Environmentally ♦ Slowdrying ♦ IJ02, IJ04, IJ21, pigment typically contains: friendly ♦Corrosive IJ26, IJ27, IJ30 water, pigment, ♦ No odor ♦ Pigment may clog♦ Silverbrook, EP surfactant, humectant, ♦ Reduced bleed nozzles 0771658 A2 and and biocide. ♦ Reduced wicking ♦ Pigment may clog relatedpatent Pigments have an ♦ Reduced actuator applications advantage inreduced strikethrough mechanisms ♦ Piezoelectric ink- bleed, wicking and♦ Cockles paper jets strikethrough. ♦ Thermal ink jets (with significantrestrictions) Methyl MEK is a highly ♦ Very fast drying ♦ Odorous ♦ AllIJ series ink jets Ethyl volatile solvent used ♦ Prints on various ♦Flammable Ketone for industrial printing substrates such as (MEK) ondifficult surfaces metals and plastics such as aluminum cans. AlcoholAlcohol based inks ♦ Fast drying ♦ Slight odor ♦ All IJ series ink jets(ethanol, can be used where the ♦ Operates at sub- ♦ Flammable2-butanol, printer must operate at freezing and temperatures belowtemperatures others) the freezing point of ♦ Reduced paper water. Anexample of cockle this is in-camera ♦ Low cost consumer photographicprinting. Phase The ink is solid at ♦ No drying time- ink ♦ Highviscosity ♦ Tektronix hot melt change room temperature, and instantlyfreezes on ♦ Printed ink typically piezoelectric ink jets (hot melt) ismelted in the print the print medium has a ‘waxy’ feel ♦ 1989 Nowak headbefore jetting. ♦ Almost any print ♦ Printed pages may U.S. Pat. No.4,820,346 Hot melt inks are medium can be used ‘block’ ♦ All IJ seriesink jets usually wax based, ♦ No paper cockle ♦ Ink temperature with amelting point occurs may be above the around 80° C. After ♦ No wickingoccurs curie point of jetting the ink freezes ♦ No bleed occurspermanent magnets almost instantly upon ♦ No strikethrough ♦ Ink heatersconsume contacting the print occurs power medium or a transfer ♦ Longwarm-up time roller. Oil Oil based inks are ♦ High solubility ♦ Highviscosity: this ♦ All IJ series ink jets extensively used in medium forsome is a significant offset printing. They dyes limitation for use inhave advantages in ♦ Does not cockle ink jets, which improved paperusually require a characteristics on ♦ Does not wick low viscosity. Somepaper (especially no through paper short chain and wicking or cockle).multi-branched oils Oil soluble dies and have a sufficiently pigmentsare required. low viscosity. ♦ Slow drying Micro- A microemulsion is a ♦Stops ink bleed ♦ Viscosity higher All IJ series ink jets emulsionstable, self forming ♦ High dye solubility than water emulsion of oil,water, ♦ Water, oil, and ♦ Cost is slightly and surfactant. Theamphiphilic soluble higher than water characteristic drop size dies canbe used based ink is less than 100 nm, ♦ Can stabilize ♦ High surfactantand is determined by pigment concentration the preferred curvaturesuspensions required (around of the surfactant. 5%)

I claim:
 1. A method of manufacturing an ink supply print head whichejects ink via the utilization of thermal actuator devices, the methodcomprising the steps of: (a) providing a silicon and circuitry waferlayer including electrical circuitry necessary for the operation ofthermal actuator devices on demand; (b) depositing a first sacrificiallayer on top of the silicon and circuitry wafer layer; (c) forming aseries of heater structure layers defining the thermal actuator deviceson top of the first sacrificial layer; (d) depositing a secondsacrificial layer on top of the heater structure layers, the secondsacrificial layer including etched portions suitable for forming nozzlechambers; (e) depositing a third sacrificial layer to define nozzlechambers, each nozzle chamber having an ink ejection port positionedabove the second sacrificial layer; (f) back etching the silicon waferlayer to form an ink supply channel in a region underneath a moving endof each thermal actuator; and (g) etching the first and secondsacrificial layers in addition to relevant portions of the silicon andcircuitry wafer layer, to free the thermal actuator devices.
 2. A methodas claimed in claim 1 wherein the back etching of the wafer layerincludes forming a single ink supply channel that supplies each of aplurality of nozzle chambers.
 3. A method as claimed in claim 2, whereinthe third sacrificial layer is formed so that the nozzle chambers eachhave side wall portions and a top wall portion, with the side wallportions dividing the ink supply channel into multiple supply channels.4. A method as claimed in claim 1 wherein the heater structure layersare formed by the steps of: (a) depositing a first expansive materiallayer having a first coefficient of thermal expansion on the firstsacrificial layer; (b) depositing a conductive heater layer on the firstexpansive material layer; and (c) depositing a second expansive materiallayer having a second coefficient of thermal expansion on the conductiveheater layer, the first coefficient of thermal expansion being greaterthan the second coefficient of thermal expansion.
 5. A method as claimedin claim 4 wherein the conductive heater layer is formed by the stepsof: (a) forming suitable trenches in the first expansive material layer;(b) depositing a conductive material over substantially the whole of thefirst expansive material layer; (c) chemically and mechanicallyplanarizing the conductive material so that the conductive heater layerremains.
 6. A method as claimed in claim 5 wherein the conductive heaterlayer is formed from substantially pure gold.
 7. A method as claimed inclaim 1 wherein metal conductive lines are incorporated into the waferlayer to form a barrier to protect the wafer layer from unwanted etchingby any sacrificial etchant utilized in etching the sacrificial layers.8. A method as claimed in claim 1 wherein the back etching step is deepsilicon trench etching of the wafer layer.
 9. A method as claimed inclaim 1 wherein the wafer layer is first passivated by depositing apassivation material on the wafer layer.
 10. A method as claimed inclaim 1 wherein the third sacrificial layer is formed to define a seriesof small etchant holes used in the etching of the other sacrificiallayers.
 11. A method as claimed in claim 1 wherein the third sacrificiallayer is comprised substantially entirely of Silicon Nitride.
 12. Amethod as claimed in claim 1 wherein the third sacrificial layer isformed to incorporate portions positioned on the heater structure layersto firmly clamp the heater structure layers to lower layers.
 13. Amethod as claimed in claim 1 wherein the wafer layer comprises adouble-sided polished CMOS wafer.
 14. A method as claimed in claim 1which includes a further step of separating the wafer layer intoseparate printhead chips.